1. Field of the Invention
The present invention relates to an electronic device for a local area electronic communications network.
2. Cross-Reference to Related Application
The subject matter of the present application is also disclosed in the copending application Ser. No. 065,229, filed June 22, 1987, assigned to the assignee of the present invention.
3. Description of the Prior Art
When multiple electronic apparatuses, whether they be computers, peripherals or servers, are interconnected in a series, or "daisy-chain". form of local area communications network the possibility exists that the failure of one of the interconnected apparatuses would result in an opening in the network and would thus incapacitate the network. An alternative form of local area network interconnection is known as the "star" configuration. In the star configuration all connections to the apparatuses interconnected into the network emanate from a central node. There is known in the art an electronic device which provides multiple connections to support multiple electronic apparatuses in a star configuration. Solely for purposes for this application, such an electronic device shall be referred to as a "concentrator", although such usage should not be confused with that term as the same is defined in Graf; Modern Dictionary of Electronics; Sams and Co., Inc.; Indiana, USA; 1977; pp. 144. As an advantage of the star configuration the possibility that the malfunction of a given one of the electronic apparatuses will result in the incapacity of the entire network is precluded.
Once they are interconnected the linked apparatuses communicate with each other over the network using some form of bit encoding scheme. One common form of coding is a frequency modulation scheme known as "FM(O)" modulation. This technique subdivides a data stream into "cells", or bit times, with the occurrence or absence of a signal transition during the bit time denoting a predetermined binary digit. The encoding scheme is such that some predetermined signal feature, such as a transition of a waveform, will occur at some recurrence rate. For example, in the instance of an FM(O) modulation scheme a rising edge will occur at least once during the time period T that encompasses two bit times. The FM(O) modulation scheme is discussed in the article "Inside Appletalk", Byte magazine, June 1985, pages 195 to 200, at pages 190 to 192.